SACRAMENTO -- Sacramento investigators are using DNA covertly collected from a cigarette in an attempt to prove a man killed his aunt, officials said.

Investigators took DNA evidence from a bloody towel found at the murder scene more than 15 years ago and are seeking to prove in court that it matches DNA from a cigarette Rolando Gallego, 49, smoked in 2006, The New York Times reported.

Gallego's lawyer, David Lynch, argues that the methods used to collect DNA evidence are unfair and shouldn't be brought to court when his client goes on trial for murder next month.

"The law cannot tolerate such back-door methods, which seize something that any reasonable person expects to remain private," Lynch wrote in a motion to not to use the DNA.

Law enforcement officials maintain the practice of "surreptitious sampling" is necessary to solving many cases.